1. Field of the Invention
This invention relates to a process for producing an ink jet recording head which performs recording by discharging ink.
2. Related Background Art
An ink jet recording head to be applied for the ink jet recording system is generally provided with a fine orifice for discharging ink, an ink pathway communicated to this discharging orifice and a discharging energy generating section provided at a part of the ink pathway. FIG. 1A is an example of the ink jet recording head of the prior art and in this Figure, the symbol 304 shows the discharging orifice, 305 the ink pathway and 306 the discharging energy generating section. On the other hand, 301 is a substrate, 302 an ink pathway wall forming member, 303 a lid plate and 307 an ink feeding inlet.
In the prior art, as such ink jet recording head, those utilizing photosensitive resin compositions have been known. For example, U.S. Pat. No. 4,417,251 discloses an ink jet recording head in which an ink pathway wall is formed by use of a photosensitive resin composition and a rigid upper lid is laminated on the ink pathway wall forming member to form an ink pathway. Also, U.S. Pat. No. 4,394,670 discloses an ink jet recording head in which an ink pathway wall is formed by use of a photosensitive resin composition and a cover of an ink pathway formed by use of a photosensitive resin composition is laminated on the ink pathway wall forming member to form an ink pathway. These ink jet recording heads utilizing photosensitive resin compositions have excellent advantages such as easy fine working by applying the so-called photolithographic technique, etc.
In producing such ink jet recording heads as described above, however, after formation of an ink pathway wall on a substrate by use of a photosensitive resin composition such as dry film, or other composition, an ink pathway is formed by laminating on the ink pathway wall forming member a rigid upper lid or a cover of an ink pathway formed by use of a photosensitive resin composition, or other composition which becomes the cover over the ink pathway. During this operation, for improving adhesiveness of the above cover over the ink pathway with the ink pathway wall forming member or effecting improvement of uniformity at the bonded interface, it is generally practiced to press the laminate under an appropriate pressure.
During such pressing, a phenomenon called "sagging" sometimes occured. This "sagging phenomenon" is of two kinds. One is the case when the above ink pathway wall is formed by use of relatively soft substances such as a photosensitive resin composition, or other soft substances, whereby the above ink pathway wall-forming member is deformed by pressing of the lid plate to give rise to "sagging" 310 as exemplified in FIG. 1B. The other case is when at least the ink pathway wall side of the lid plate is formed by use of relatively soft substance 312 such as a photosensitive resin composition, the above ink pathway wall side of the lid plate is deformed when this is pressed, to give rise to "sagging" 311 as exemplified in FIG. 1C. Further, the above two kinds of "sagging" sometimes occurred as a mixture.
Also, such "sagging" is sometimes apt to occur particularly in a multi-array type ink jet recording head having a plurality of fine ink pathways arranged, for example, having a plurality of discharging orifices over the entire paper width of a recording paper of A4 width (210 mm) and in some heads, the amount of sagging became as much as 1/3 of the total amount to exert deleterious influences on the discharging characteristic such as instability of the ink discharging direction, whereby recording characteristic was deteriorated. In addition, such "sagging" may be sometimes differed from one ink pathway to another, whereby the ink discharging performance was varied for every pathway to worsen the recording characteristic.
For prevention of such "sagging", for example, it has been attempted to arrange a supporting column for prevention of sagging within the ink pathway as disclosed in the above U.S. Pat. No. 4,394,670. However, even when such a supporting column may be provided, the sagging prevention effect is insufficient, and "sagging" frequently occurred particularly in an ink jet recording head in which fine ink pathways are arranged in a large number, thereby sometimes causing lowering in yield. Such a problem was the common problem in the processes for forming ink jet recording heads in which a part of the ink pathway was formed by use of a material having temporarily no rigidity such as photosensitive resin compositions, thermosetting resins, or other materials.